Diagnostic Test Pattern. (C55/C55Mp) - Xerox DocuPrint C55 Service Manual

Diagnostic Test Pattern. (C55/C55mp)

This test pattern can be used by the Help
Center to determine the status of some of the
machine parameters.
Process Control Status:
If Black, Cyan, Magenta, or Yellow, indicate:
Under Limit Error - Process controls thinks
the prints are too light even at the highest
bias.
Over Limit Error - Process controls thinks
the prints are too dark even at the lowest
bias.
Irregular Error - The Gamma Sensor did not
see the expected difference between the 3
patches during setup.
Possible causes for Under
Irregular errors tend to be the same:
•
Transfer Nip too small, or poor transfer in
general.
•
Toner concentration in the developer
assembly is too low. Arcing may be
causing excessive toner consumption.
•
Very low Relative Humidity. Magenta is
especially sensitive to this problem. The
error occurs if Relative Humidity is less
than 10 counts (General information on
Diagnostic sheet).
•
Developer assembly problem.
•
High Voltage Power supply problem.
Possible causes for Over Limit errors:
•
Very high Relative Humidity. The error
occurs if Relative Humidity is greater than
35 counts (General information
Diagnostic sheet).
•
Dirty white patch on transfer drum.
The toner concentration in the developer
assembly is too high.
IMAGE QUALITY SPECIFICATIONS
TEST PATTERNS
Calibration Errors occur when reading the
white patch, and the difference between full
Gamma voltage and half Gamma voltage is
not what was expected. Suspect a dirty white
patch or bad Gamma Sensor.
Density Rate Setpoints:
The default is 90, If the Density and Color
Balance has been adjusted, these setpoints
will change. The range is between 80 and
100. If the Density and Color Balance tries to
exceed a limit, the process control will indicate
an over or under error.
approximately 10 Volts of developer bias
Toner Concentration:
Setpoint - The default is 70.
developer assembly is installed, the toner
concentration sensor " reads" the new housing
Limit and
and the setpoints are entered in NVM. These
setpoints are critical for proper copy quality
and must be re-entered if the PCU PWB is
replaced or the NVM is initialized. If the NVM
is accidentally initialized, the setpoints can be
obtained from the Diagnostic sheet and re-
entered into NVM.
Control Point - This is the value that the toner
concentration
assembly tries to maintain. The control point
uses the setpoint as a starting point and then
varies depending on the temperature and
relative humidity. In high humidity conditions,
the value is increased and in low humidity
conditions, the value is decreased.
The Black value varies between − 20 to + 27.
The Color value varies between − 28 to + 22
on
One count is
When a new
sensor in the developer
2/99
3-22
Value - The values are measured by the toner
concentration sensors during the print cycle
and determine when toner needs to be added
to the developer assembly. The value usually
does not equal the control point exactly, but is
generally within 5 counts.
Process Voltage:
Transfer Bias - This is the voltage applied to
the transfer drum.
The Paper default is 1305V and varies
depending on the temperature and relative
humidity. In high humidity conditions, the
value is decreased and in low humidity
conditions, the value is increased.
The Paper bias varies between 1200-1400V.
The Transparency default is 2000V and
varies depending on the temperature and
relative humidity. The voltage varies for each
of the 4 colors when running transparencies.
Black default is 2000V
Cyan default is 2200V
Magenta default is 1400
Yellow default is 2600
As the humidity changes the voltage is also
changed to compensate.
Developer Bias - The default bias is 400V.
The four developer bias voltages are set
during the Process Control cycle at power on.
The voltage range is from -250 to -550 volts.
In general, the higher the bias the darker the
print. If the values get too high or too low, the
charge voltage may change to compensate.
The Magenta voltage tends to be higher.
These values will also change when the color
balance procedure is performed.
DocuPrint C55/C55mp